1. Field of the Invention
The present invention relates to a frame transfer apparatus and a frame transfer method, and more particularly to a frame transfer apparatus and a frame transfer method within a network system in which device information is transmitted in multicast at an L2 layer.
2. Description of the Related Art
While various terminals are connected to a network, and the inside of a Local Area Network (LAN) is more complicated, a method for automatically collecting information of terminals or the like within the network, or an Link Local Discovery Protocol (LLDP) has been devised by an IEEE 802.1AB.
The LLDP is used within the LAN as a protocol of a link layer (L2 layer). Each terminal and a frame transfer apparatus within the network sends its own device information as an LLDP frame to a destination multicast address over the network. If the frame transfer apparatus receives a frame of the destination multicast address, the frame is transferred to every port except for a reception port. Therefore, an LLDP frame sent from each terminal and the frame transfer apparatus is delivered to all the terminals within the network. Thereby, the information of each terminal within the network can be automatically collected by collecting the LLDP frame sent by each terminal and the frame transfer apparatus. Also, a Time To Live (TTL) is defined in the LLDP, whereby each terminal for sending the LLDP frame can make a survival confirmation for the terminal by sending the LLDP frame at a shorter period than the TTL.
In the LLDP, a multicast address is designated in a destination MAC address of the LLDP frame. Therefore, the LLDP frame is sent to a terminal not needing to receive the LLDP frame, unnecessarily pressing a network band. Also, in an IEEE802.1d as defined before the IEEE802.1AB, the MAC address of destination multicast defined by the IEEE802.1AB is provided in an address range subjected to frame destruction. Therefore, there is a problem that if a frame transfer apparatus not supporting the IEEE802.1AB is present within the network, the LLDP frame does not arrive at the terminal connected to the frame transfer apparatus. To improve this problem, the frame transfer apparatus for transferring the LLDP frame in which the destination MAC address is converted from the multicast address to a unicast address is disclosed in JP-A-2008-172381. Thereby, it is possible to send the LLDP frame to only the terminal needing to receive the LLDP frame, preventing the network band from being pressed due to unnecessary LLDP frame. Also, if a bridge not supporting the IEEE802.1AB is present within the network, it is possible to send the LLDP frame to the terminal connected to the concerned bridge as well, because the unicast address is designated in the destination MAC address.